intended to be dissolved slowly in the mouth, but to be swallowed with or without previous mastication.

Lozenges intended for immediate use do not require much drying, but those intended for stock must be thoroughly dried before they are put away in glass containers, otherwise they are liable to soften and adhere, and may even become mouldy. The drying is best effected on perforated trays in a moderately warm room. To avoid cracking of the edges, which will sometimes occur when lozenges are dried, the addition of a small quantity of glycerin to the water used will be found advantageous, and does not interfere with proper desiccation.

The average weight of lozenges is between 0.650 and 1.30 Gm. (10 and 20 grains), although in the nine working formulas of the Pharmacopoeia the weight is found to vary between 0.40 and 0.96 Gm. (6 and 15 grains).

The following is a list of the official lozenges, showing the composition and excipient used:

46

CHAPTER XXX.

COMPRESSED TABLETS AND TABLET TRITURATES.

COMPRESSED TABLETS.

THIS class of remedies, allied to lozenges, under the name compressed pills," was introduced into England nearly sixty years ago, and some years later into this country. The former name, although in a measure erroneously applied, because pills are understood to be made from a previously prepared plastic pill-mass, is still used by one or two manufacturers. Compressed tablets are lenticular-shaped disks containing one or more medicinal agents, and are obtained by compressing the material in the form of a granular powder into suitable shape by means of specially constructed apparatus operated by hand, steam, gas, or electric power.

Compressed tablets, although greatly in favor among physicians, for many years left much to be desired, and it is doubtful whether their extended use was justified, since the firm compression rendered many of them slowly soluble, while those containing insoluble substances failed to break up in water or the fluids of the stomach, even after hours of contact, so that the action of such tablets was either very much retarded or altogether prevented. Of late years, however, great improvements have been made in this respect, and compressed tablets are now made in such form that they will disintegrate within a few seconds when placed in water. This rapid and complete disintegration is especially desirable for such insoluble substances as bismuth subnitrate, bismuth subgallate, calcined magnesia, quinine sulphate, and various combinations of these with other substances. Its achievement must be admitted to be a decided and valuable improvement, and the process by which it is done is quite simple. The admixture of powdered starch with the granulated mixture as it is being fed into the compressor is known to impart to the tablet its disintegrating property, the exact quantity of starch necessary varying with different combinations. It is possible that manufacturers employ other agents in addition to starch, with a view to increasing the rapidity of disintegration of the tablets; but if so, such additions are not made public, and the secret is strictly guarded; plain starch, however, has been found very efficient. In addition to this improvement, the ready portability of compressed tablets, their convenient dosage, and comparative taste

lessness when swallowed, together with their stability when properly made and kept, have at the present day increased their manufacture and use to an enormous extent. The fact that compressed tablets may be readily sugar-coated or chocolate-coated has also added much to their popularity. The variety of combinations of medicinal agents capable of being presented in this form is practically without limit. Nevertheless not all medicaments are suitable for preparation into compressed tablets. This is especially the case with very volatile or readily oxidizable substances, since in the necessary exposure of the material during its preparation for compression considerable loss by volatilization is likely to occur, as in the case of camphor, or the material is changed by oxidation, as in the case of phosphorus. For such substances a well-made pill properly protected by a coating is to be preferred.

It is manifestly impossible to give complete working directions for the preparation of every possible combination of remedial agents into compressed tablets, and much must be left to the judgment of the operator as each case presents itself. The general principles underlying this branch of pharmaceutical manipulations, however, are elucidated here. The first object must be to obtain the material to be compressed in the condition of a fairly uniform granular powder, a No. 20 or No. 30 granule being the usual degree of fineness employed. Fine powders are not adapted for compression, since the air which they carry with them when fed into the die is confined in the interstices between the particles, and cannot escape upward or downward during compression between the closely fitting dies and punches, hence imperfect compression results; moreover, fine powders have a tendency to cake or pack closely, and therefore do not feed regularly into the die. They also have a greater tendency to adhere to the surfaces of the punches and the sides of the die than does the same material in a granular form.

When the tablet to be compressed is to contain a single medicinal substance, this can often be bought in a granular form from the wholesale dealer, as, for instance, potassium chlorate, potassium, sodium, and ammonium iodides, bromides, and chlorides, potassium permanganate, sodium phosphate, zinc sulphate, etc. In such cases it is only necessary to reduce the commercial granular powder to a more uniform condition by passing it through a clean No. 20 iron sieve. No excipient whatever is necessary for these substances, although at times it may be necessary to subject the material to the action of dry, warm air for a short time, in order to free it from accidental moisture. When salts containing water of crystallization are to be compressed alone and require previous drying, care must be taken not to expel any of this water. Sometimes crystallized salts may be reduced to the proper granular condition by simply grinding them in a mill.

Greater difficulty is experienced and more care must be exercised

when two or more substances, either all medicinal or part medicinal and part diluent or excipient, are to be mixed and granulated. In such cases all ingredients should be in the form of a fine powder. If potent remedies are to be incorporated, they should be thoroughly triturated either with the diluent or with the other ingredients, and the mixture should then be passed through a No. 80 bolting-cloth sieve, and again well mixed after sifting. The mixture is then moistened with whatever fluid or mixture of fluids the medicinal constituents or the diluents or excipients may dictate. The moistening fluid may be water, alcohol, a mixture of alcohol and water in various proportions, or aqueous solutions of glucose of different strengths. Glycerin should never be used, since it does not dry out and has a tendency to render the granules sluggish when feeding into the die. The fluid should be carefully and uniformly distributed through the entire mass, and in most instances only a sufficient quantity should be used to produce a well-moistened powder. This is then pressed through a No. 12 or No. 16 brass, iron, or tinnediron wire sieve. The choice of the size and kind of sieve will depend on the physical and chemical properties of the material being operated upon, and these properties may render it necessary to omit the passing of the moist powder through a sieve altogether. This is the case when any constituent of the mixture is likely to be affected by the metallic surface of the sieve, as, for instance, the various mercurials, salicylates, etc. Sometimes also the components when moistened form too tough a mass to permit its being forced through a sieve. In such cases the material is dried out immediately after having been moistened, and is then ground in a mill or a mortar to the proper granular condition. The moistened powder which has been forced through a sieve is spread on glass plates or sized paper, and dried by exposure to either ordinary or warmed air. The physical and chemical properties of the substance will again dictate the conditions under which this drying should be conducted. Readily fusible (salol) or volatile (camphor, benzoic acid, essential oils, etc.) substances should be dried in the cold. When small quantities of volatile substances, as, for instance, flavoring oils, etc., are to be incorporated, they may be omitted from the mass and subsequently sprayed over the dried granules after having previously been dissolved in a little alcohol or ether. The granules should then again be carefully mixed. Most substances permit drying by means of circulating warm air, and all such as are readily affected by light should be carefully protected during drying. The dried granules are now forced through a No. 20 or No. 30 sieve. If during this operation much fine powder has been produced, it may be necessary to separate the same by means of a fine sieve and to regranulate it.

Sometimes it is necessary to add to the granular powder a lubricant, preferably the best quality of liquid petrolatum, in order to enable the tablet to be more readily expelled from the die. Usually